Bivalent Adenylate Cyclase (Cya)-Based Therapeutic Vaccines: Eradication Of Tumor Cells Expressing Different Antigens Over Time

Introduction: ProCervix is a clinical stage HPV16 E7/HPV18 E7 bivalent adenylate cyclase (CyaA)-based therapeutic vaccine targeting HPV16/18 infection in women prior to cervical high grade lesion development. We report here on the ability of ProCervix to induce E7-specific CD8+ T lymphocytes which can be both functional effector and memory cytotoxic CD8+ T lymphocytes with (CTL) and we bring the proof of concept that co-delivery of HPV16 E7 protein with non-viral Ag including OVA or MAGE-A3 result in an effective therapeutic effect while providing broad prophylaxis. Methods: Three vaccines bearing oncogenes or model Ag were prepared, ProCervix (CyaA-HPV16 E7 and CyaA-HPV18 E7), CyaA-HPV16 E7/CyaA-MAGEA3 and CyaA-HPV16 E7/CyaA-OVA. ProCervix was adjuvanted with imiquimod 5% cream applied on the skin dermis at the injection site, or admixed with Poly-ICLC (Oncovir, USA). The two other vaccines were adjuvanted with Poly-ICLC. All vaccines were injected intradermally in C57BL/6 mice. Induction of E7-specific CD8+ T cells was evaluated by IFN-γ ELISpot and E7-specific memory CTL by in vivo killing. Therapeutic efficacy was performed in TC-1 tumor bearing mice (expressing HPV16 E7). The evaluation of memory to HPV18 was subsequently performed in TC-1 tumor-free mice rechallenged with a newly engineered LL2 cell line expressing HPV18 E7. Dual vaccination effects were further evaluated with 2 vaccine combinations in TC-1-tumor bearing mice, CyaA-HPV16 E7/CyaA-OVA (EG7 rechallenge) or CyaA-HPV16 E7/CyaA-MAGEA3 (B16-MAGEA3 rechallenge). Results: ProCervix adjuvanted by Imiquimod 5% cream or Poly-ICLC produced similar therapeutic efficacy. ProCervix-vaccinated mice developed a long-lasting HPV16 E7-specific CD8+ T cell response leading to HPV16 E7-expressing tumor eradication. Functional HPV18 E7-specific memory CTL were also identified in these mice leading to the Ag-specific protection against a challenge with HPV18 E7-expressing tumor cells. Similar results were observed with eradication of TC-1 tumors followed by Ag-specific tumor no takes of either EG7 or B16-MAGEA3, with CyaA-HPV16E7/CyaA-OVA and CyaA-HPV16 E7/CyaA-MAGEA3 vaccinations, respectively. Conclusion: CyaA technology is amenable to multivalent/multi-Ag therapeutic vaccination approaches as shown by the sequential successful T-cell based therapy, and the protective memory achieved in an Ag-specific fashion. We could anticipate that ProCervix-treated patients could clear their HPV16 infection while being protected against a later infection with HPV18. This dual mechanism opens the possibility to protect/treat patients with several different Ag for a given cancer with appropriately designed CyaA-based therapeutic vaccine. Citation Format: Michael Esquerre, Marie Momot, Anne Goubier, Yolande Misseri, Marie-Christine Bissery. Bivalent adenylate cyclase (CYA)-based therapeutic vaccines: eradication of tumor cells expressing different antigens over time. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2507. doi:10.1158/1538-7445.AM2015-2507